Microcarriers provide an alternative for large-scale cell culture. Microcarriers are typically stirred in cell culture media and provide a very large surface to area ratio for cell growth. Microcarriers can provide substantially higher cell yields per culture volume relative to conventional equipment.
Some microcarriers have been prepared to present specific polypeptide sequences at the surface, which polypeptides are configured to provide specific interaction with adhesion receptors of the cells. Examples of such microcarriers include gelatin or collagen linked to dextran beads or to polystyrene beads. While having various advantages, such microcarriers are made of animal derived materials and are not suitable for culturing cells dedicated to cell therapies due to the risk of xenogenic contamination through, for example, pathogen proteins or viruses.
To solve this issue, recombinant proteins or polypeptides have been synthesized and coated onto microcarriers. While such microcarriers have the advantage of being free of animal derived components, they may not have several drawbacks. For example, the level of cell adhesion with some of these beads may not be sufficiently high for robust culture of some anchorage-dependent cells, particularly when serum free media is used. When serum-free media are used, the media do not provide adhesion proteins, which can bind to the microcarrier surface and thus facilitate binding of cells. The absence of serum especially presents problems when using cells that produce little extracellular matrix, such as certain stem cells, including embryonic stem cells.